1. Field of the Invention
The invention relates to reactive solders and brazes.
2. Discussion of the Related Art
Solders and brazes include metallic compositions used to bond components, e.g., electrical or optical components. The metallic compositions have an elemental-metal or an alloy-metal matrix. The metallic matrices of solders have low melting temperatures, i.e., lower than about 450° C. The metallic matrices of brazes have higher melting temperatures than those of solders, and thus, form more thermally resistant bonds.
Metallic matrices of simple solders and brazes do not readily form chemical bonds with ceramic surfaces. Thus, soldering or brazing to such surfaces often results in low reliability bonds. For more reliable bonding to ceramics, reactive solders and brazes were developed. In reactive solders and brazes, reactive atoms are dispersed in the metallic matrix. The reactive atoms reduce ceramic and/or semiconductor surfaces so that atoms of such surfaces are able to chemically bond with the metallic matrix of the solder or braze.
In reactive solders and brazes, the reactive atoms are typically either group IIIB or IVB elements or rare earth elements. These elements have high affinities for elements found in ceramics, e.g., oxygen, carbon, nitrogen, or fluorine. Thus, the reactive elements reduce ceramic surfaces to form stable compounds. After being reduced, ceramic surfaces more readily form chemically bonds with the metallic matrix atoms of solders and brazes.
Unfortunately, the reactive elements used in solders and brazes easily oxidize and tend to cause oxide skins to form on the solders and brazes when heated or melted. The oxide skins prevent reactive solders and brazes from wetting surfaces to be bonded. The oxide skins also impede the diffusion of reactive atoms from the interiors of solders and brazes to the surfaces to be bonded. Thus, the formation of oxide skins interfere with the bonding of reactive solders and brazes.
An oxidation-resistant reactive solder or braze is a reactive solder or braze that has a lower concentration of reactive atoms at surfaces of the solder or braze's metallic matrix than in the interior region of the metallic matrix. The oxidation-resistant reactive solders and brazes have improved wetting and bonding properties, because the lower surface concentration of reactive atoms at surfaces reduces the tendency for such solders and brazes to form oxide-skins during initial stages of soldering or brazing. After such a solder or braze melts, the reactive atoms diffuse from the interior region to the surfaces of the solder or braze. Thus, the reactive atoms are available to reduce the surface to be bonding after initial stages of soldering and brazing.
It would be useful to have new or improved methods for producing oxidation-resistant reactive solders and brazes.